It was not the spark time period that increased, it was the persistence time of that larger fireball of plasma created by the more powerful spark. When a larger amount of the plasma is created it lasts a bit longer.

 

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Maybe, just maybe in the open air, but under combustion chamber conditions?? How did you get it to increase the spark time period? I trust this guys opinions been there did that, you I don't trust so much, I've seen to many of your answers.

When I said, "I trust this guys opinions been there did that", I forgot to put in the link explainig the difference of the CDI vs HEI ignitions. http://www.superchevy.com/how-to/45618-inductive-cd-ignitions-basics/

 

It was not the spark time period that increased, it was the persistence time of that larger fireball of plasma created by the more powerful spark. When a larger amount of the plasma is created it lasts a bit longer.

Again my meter is reading in the red. That may be so on planet Michigan but not in the rest of the world.

EDIT. @MisterBill2, Plasma is just a very small amount of time in an ignition spark, it's very fast and if hot enough creates a "flame kernel" that actually ignites the cylinder fuel charge. No matter how the spark is created. If you would take some time to research this stuff, instead of just making nonsense statements your credibility would be higher. There are many papers online about this. Your anecdotes about how you did things in your youth are just not up to the data available today. Not throwing stones as you always say just presenting things as the research shows and what works.

 

When I said, "I trust this guys opinions been there did that", I forgot to put in the link explainig the difference of the CDI vs HEI ignitions. http://www.superchevy.com/how-to/45618-inductive-cd-ignitions-basics/

any chance of posting the document? The website isn't visible from Europe.

 

any chance of posting the document? The website isn't visible from Europe.

It has a lot of pictures and I'm not sure how to do it because of them. Screen shot doesn't work. If you can tell me how to do it, I'll try it. Would a VPN on your side work to get around the problem?

 

Don't know if this works. It gives the text but not the pictures.

 

Could someone enlighten me as to which circuit is used in a modern petrol engine? Although I'm familiar with the Kettering circuit in vintage cars, I've driven diesels for the last 20 years, and probably haven't looked under the bonnet of a petrol engined car since 1999.

 

Don't know if this works. It gives the text but not the pictures.

Thanks. I get the gist of it.

 

Could someone enlighten me as to which circuit is used in a modern petrol engine?

Most every engine today uses a form of "coil on/at plug" or DIS(Distributorless Ignition System) also known as muticoil ignition. Each plug has its own coil controlled by the ECM. The coils themselves are mostly E coils with a center gap, those were part of the HEI format, to allow higher magnetic saturation of the coil. I say it as coil near plug because that is what we made at Delphi/Packard, we made the very short plug wires for them. http://www.autotap.com/techlibrary/understanding_multi-coil_ignition_systems.asp

 

Most every engine today uses a form of "coil on/at plug" or DIS(Distributorless Ignition System) also known as muticoil ignition. Each plug has its own coil controlled by the ECM. The coils themselves are mostly E coils with a center gap, those were part of the HEI format, to allow higher magnetic saturation of the coil. I say it as coil near plug because that is what we made at Delphi/Packard, we made the very short plug wires for them. http://www.autotap.com/techlibrary/understanding_multi-coil_ignition_systems.asp

Thanks for that. I'd heard of coil-on-plug. So it is still an inductive discharge system.

 

So it is still an inductive discharge system

Yes. For cars even most race cars it is still the best and easiest system. Other than motorcycles I know of nothing from an OEM using a CDI or other form of ignition. Motorcycles other than off road, dirt bikes don't even use a CDI. No matter what some other responders to this thread seem to think. Drag race engines use a MSD box but not for the CDI part, they use it because of the easy rev limit circuit. If CDI was so good why doesn't a top fuel or funny car use them? They use magnetos, usually twin mags. One feeding a plug on either side of the piston, needed because they are hemispherical cylinder heads with a very high compression and no line of sight to both sides when the ignition fires.

 

I can see that a gapped E-core would offer some improvement - the usual "ignition coil" is hardly the best core shape for efficiency! I presume that it still a laminated silicon-iron core.
Magnetos have one huge advantage - output increases with speed, whereas on Kettering, the opposite is true and "dwell time" actually decreases as speed increases.
I presume on a modern petrol engine the engine management computer has complete control over "dwell time" (and it probably been given it a new name)

 

What I am trying to do basically is create a rudimentary 600V power source which can give short blasts of ~600V and high currents at high frequencies.

Multi spark in capacitor system @600V:

 

the usual "ignition coil" is hardly the best core shape for efficiency! I presume that it still a laminated silicon-iron core.

Yes the change from a "can" style coil to an "E" coil is what allowed the HEI type ignition finally take off. Whe GM first used HEI it was with the old can type coils, wasnt much of a step up from points othere than less wear and points problems. All of the OEM at least American ones use a form of HEI, it HEI, it just a copyright name from GM.

QUOTE="Ian0, post: 1646691, member: 719943"]
I presume on a modern petrol engine the engine management computer has complete control over "dwell time" (and it probably been given it a new name)
[/QUOTE]

I don't know if they still use the phrase Dwell but they probably do. Until they went to DIS, the last true HEI from GM used the ECM to control dwell time and advance/retard that was done with the old vacuum advance can on the distributor. The module is commonly called a 7 pin module. For most part when using a HEI for other than a replacement people are better of using the older 4 pin without all the bells and whistles of the 7 pin. There are lots of links out there showing how to do it. Some even use a Ford Duraspark version of the HEI.

 

So, by the time we get to post #100, should we be recommending to the TS that he gives up the idea of CD and gets a HEI E-core coil?

 

I am open to anything really but I will have a distributor so I'm just not sure how that would work out with a multi spark TSI system. I also have been working on my own, drew up some boards and ordered them from JLCPCB so that'll be fun. This is for a CDI system.

 

Yes the change from a "can" style coil to an "E" coil is what allowed the HEI type ignition finally take off. Whe GM first used HEI it was with the old can type coils, wasnt much of a step up from points othere than less wear and points problems. All of the OEM at least American ones use a form of HEI, it HEI, it just a copyright name from GM.

That explains something else that has been puzzling me - Ignition IGBTs - I'd always thought that a Vcs(sat) of 1.8V might be a bit of a problem. I remember when I made my circuit with a BU208 horizontal-scan transistor (with a Hfe of 7) and a Baker clamp, I thought Vce(sat) of 0.6V was rather a lot, but when you have a lot less R for the same amount of I^2L then perhaps it isn't a problem after all.

 

So, by the time we get to post #100, should we be recommending to the TS that he gives up the idea of CD and gets a HEI E-core coil?

That is what I've been saying right along, but no one listened to me. CDI sounds good when bench racing but almost no one actually uses them on multi cylinder engines. They just use a MSD-6 or something similar for the rev limiter( to protect the expensive engine if there is a drive line failure or traction problem) and for the contingency payouts if you win.

CDI is usually brought up by those that aren't into real performance and how to get it. Sorry if that offends people, but it is the truth. There are better ways to spend money for performance, ways that work.

 

I'd always thought that a Vcs(sat) of 1.8V might be a bit of a problem.

Do you mean to say that or did you mean to say, Vce(sat)?

You do understand that even though a car it's self is 12V the outputs from any of the computers/modules is ~5V or some times less, as are the inputs to the control modules from most of the sensors in the car.

 

Yes - I did mean Vce(sat) - 1.8V is a lot to lose from a 12V supply - it only leaves 10.2V across the coil, but if the series resistance of the coil is much lower it won't be the limiting factor.

It's taken me a while to catch up with what's under the bonnet of a modern petrol-engined car! I was favouring CDI before I read the article I quoted in post #18.
https://worldradiohistory.com/UK/Wireless-World/90s/Electronics-World-1997-12.pdf
starting at page 16.